The invention relates to a light-emitting diode having a code, particularly for different light intensity classes, and having a connection element with at least two electrical contact elements for connecting a power supply.
Such light-emitting diodes (LED) are frequently used in practice for illumination in the area of the dashboard of a motor vehicle and serve as a signal or monitor light, for example, but also, to an increasing extent, for illuminating instrument dials. Light-emitting diodes are used in preference on account of their low susceptibility to faults in comparison to incandescent lamps, as well as their relatively low power consumption. Contributions in this area have been provided not only by the achievement of virtually any desired colors, but also, above all, by a considerable increase in light intensity. It is already possible to obtain light-emitting diodes whose light intensity is sufficient for motor vehicle brake lights to be equipped with them, for example.
Difficulties with the use of light-emitting diodes are, in practice, caused by the light intensity, which cannot be defined exactly in advance in the manufacturing process. Hence, the light intensities of different diodes, which may even come from the same batch, for example, fluctuate despite constant voltage and current consumption. This causes considerable problems, depending on the area of application. For example, reading accuracy is impaired in those display devices equipped with such light-emitting diodes, and these fluctuations in the brightness of a number of light-emitting diodes arranged next to one another create an inferior impression.
Attempts have hitherto been made to counter this problem by measuring the light intensity of the different light-emitting diodes during the manufacturing process and then providing the light-emitting diodes with a code denoting the light intensity class. In this context, the code usually comprises a bar code which is attached to the light-emitting diode or to a connection element connected to the light-emitting diode. When the light-emitting diode is being fitted, the code is then read first of all and, depending on the light intensity class, a series resistor is selected and connected upstream of the light-emitting diode, so that the light intensity of different light-emitting diodes of one type is guaranteed to be approximately constant.
In this case, a particular disadvantage is the considerable effort which is necessary to detect the bar code and then to connect an appropriate series resistor upstream of the light-emitting diode. Furthermore, in the event of any replacement being necessary, the series resistor and the light-emitting diode always have to be replaced together on account of being individually matched to one another. Alternatively, additional outlay is involved in the manufacture of the component having the light-emitting diode, since the light-emitting diode and the corresponding series resistor form an inseparable unit.
It might be conceivable to integrate an appropriate series resistor during the actual manufacture of the light-emitting diode. However, this causes the range of applications to be limited straight away by the change in dimensions compared with known light-emitting diodes, in particular.